Fisheries bycatch data provide insights into the distribution of the mauve stinger (Pelagia noctiluca) around Ireland

There is concern that jellyfish populations are proliferating in the Northeast Atlantic and that their socio-economic impacts will increase. Using information from the Irish Groundfish Survey, data are presented on the distribution of the mauve stinger, Pelagia noctiluca, over an area >160 000 km² around Ireland and the UK in 2009. The species accounted for 93% of the overall catch of gelatinous organisms, with an average catch biomass of 0.26 ± 2.3 kg ha−1. The study area was divided into four subregions (North, West, Southwest, and South), and the distribution and abundance of P. noctiluca displayed both inter- and intraregional variations. Individual bell diameters ranged from 1 to 13.5 cm (median 4.5 cm, s.d. 1.2 cm), and the size distribution also varied spatially. It is the first time that such detailed information has been made available for P. noctiluca in a part of the Northeast Atlantic where its impact on the salmon aquaculture industry can be considerable. Finally, the possibility of using annual datasets from this type of fisheries survey to develop time-series that, in the future, will allow investigation of relationships between long-term variations of P. noctiluca populations and climatic factors in the area is addressed.

Long-term trends in the Australaian gannet (Morus serrator) population in Australia: the effect of climate change and commercial fisheries

The Australasian gannet (Morus serrator) population has increased considerably over the past century, both in New Zealand and Australia. Since 1980, the population in Australian waters has increased threefold, from 6,600 breeding pairs to approximately 20,000 pairs in 1999-2000, a rate of 6% per year. Reasons for the increase in the Australasian gannet population are poorly understood; here we consider the possible effects of recent fluctuations in climatic and oceanographic conditions, and changes in major local commercial fisheries. A significant trend towards more frequent, and stronger, El Niño Southern Oscillation events, warmer summer sea surface temperatures in Bass Strait, increased annual catches and catch per unit effort in the Victorian pilchard (Sardinops sagax) fishery and potential increased discarding of fisheries bycatch may account for at least some of the observed increase in the Australasian gannet population. The potential interactive effects of these factors on prey distribution and abundance and consequently on gannet numbers are discussed.

Comparing external and internal dorsal-spine bands to interpret the age and growth of the giant lantern shark, Etmopterus baxteri (Squaliformes: Etmopteridae)

The giant lantern shark, Etmopterus baxteri, is taken as bycatch of commercial fisheries that operate in deepwater off southeastern Australia. Bands on the second dorsal spine were used to obtain age estimates. The number of bands on the external surface of the spine and within the inner dentine layer increased with animal length. Most spines had more bands on the external surface, and the rate of band formation was significantly different between the external surface and the inner dentine layer. Females had a maximum of 57 external bands and 26 internal bands, while males had up to 48 external bands and 22 internal bands. Age estimates from external bands suggest maturity (A ₅₀) at 20 years for males and 30 years for females. Internal band age estimates suggest maturity at 10.5 years for males and 11.5 years for females. Although there is a large discrepancy between these two preliminary (i.e., unvalidated) age estimates, they both suggest that E. baxteri is a long-lived and late maturing species that is likely to be susceptible to over fishing.

Reproductive biology of the eastern shovelnose stingaree Trygonoptera imitata from south-eastern Australia

Abstract. In applying a quantitative approach to the reproduction of Trygonoptera imitata, the present study contributes to understanding the wide diversity in the reproductive biology of the family Urolophidae and provides insights to help determine phylogenetic relationships. This localised species is taken as bycatch in several inshore fisheries and potentially impacted by a range of other anthropogenic pressures, including introduced species, particularly in shallow-water pupping areas.T. imitata can be characterised as a species of comparatively lowmatrotrophic histotrophy with an extended period of relatively large eggs in utero (5–8 months) followed by rapid growth of the embryos (4–6 months). The reproductive cycle is annual with parturition occurring during late-February–April, followed immediately by ovulation. Mean size-at-birth is ~225mm total length and there is a ~1000% gain in mean wet mass from egg (15 g) to full-term embryo in utero (150 g), the lowest reported for any viviparous batoid. Litter size increases with maternal length, reaching a maximum of seven, and sex ratio of embryos is 1 : 1. Maximum length and estimates of the maturity–ogive parameters l₅₀ and l₉₅ are similar for females and males.

Satellite telemetry suggests high levels of fishing-induced mortality in marine turtles

Long-term records of nesting numbers, or proxies to nesting numbers, show a precipitous decline in the size of many sea turtle populations. Population declines are most frequently attributed to fisheries bycatch, although direct quantification of this level of mortality is rare. We used satellite-tracking records for turtles in the Mediterranean Sea and Pacific, Atlantic and Indian Oceans to identify when turtles had been captured. Evidence for capture came from a combination of an increase in good quality locations from transmitters, transmitters moving inland to coastal towns and villages, and on-board submergence data, showing that transmitters had come out of the water. A high level of mortality was calculated, confirming current concerns regarding the outlook for sea turtles.

The biology and ecology of the ocean sunfish Mola mola : a review of current knowledge and future research perspectives

Relatively little is known about the biology and ecology of the world’s largest (heaviest) bony fish, the ocean sunfish Mola mola, despite its worldwide occurrence in temperate and tropical seas. Studies are now emerging that require many common perceptions about sunfish behaviour and ecology to be re-examined. Indeed, the long-held view that ocean sunfish are an inactive, passively drifting species seems to be entirely misplaced. Technological advances in marine telemetry are revealing distinct behavioural patterns and protracted seasonal movements. Extensive forays by ocean sunfish into the deep ocean have been documented and broad-scale surveys, together with molecular and laboratory based techniques, are addressing the connectivity and trophic role of these animals. These emerging molecular and movement studies suggest that local distinct populations may be prone to depletion through bycatch in commercial fisheries. Rising interest in ocean sunfish, highlighted by the increase in recent publications, warrants a thorough review of the biology and ecology of this species. Here we review the taxonomy, morphology, geography, diet, locomotion, vision, movements, foraging ecology, reproduction and species interactions of M. mola. We present a summary of current conservation issues and suggest methods for addressing fundamental gaps in our knowledge.

Thermal niche, large-scale movements and implications of climate change for a critically endangered marine vertebrate

Climate change is expected to have a number of impacts on biological communities including range extensions and contractions. Recent analyses of multidecadal data sets have shown such monotonic shifts in the distribution of plankton communities and various fish species, both groups for which there is a large amount of historical data on distribution. However, establishing the implications of climate change for the range of endangered species is problematic as historic data are often lacking. We therefore used a different approach to predict the implications of climate change for the range of the critically endangered planktivourous leatherback turtle (Dermochelys coriacea). We used long-term satellite telemetry to define the habitat utilization of this species. We show that the northerly distribution limit of this species can essentially be encapsulated by the position of the 15°C isotherm and that the summer position of this isotherm has moved north by 330 km in the North Atlantic in the last 17 years. Consequently, conservation measures will need to operate over ever-widening areas to accommodate this range extension.

Flexible foraging movements of Leatherback turtles across the North Atlantic Ocean

Some marine species have been shown to target foraging at particular hotspots of high prey abundance. However, we show here that in the year after a nesting season, female leatherback turtles (Dermochelys coriacea) in the Atlantic generally spend relatively little time in fixed hotspots, especially those with a surface signature revealed in satellite imagery, but rather tend to have a pattern of near continuous traveling. Associated with this traveling, distinct changes in dive behavior indicate that turtles constantly fine tune their foraging behavior and diel activity patterns in association with local conditions. Switches between nocturnal vs. diurnal activity are rare in the animal kingdom but may be essential for survival on a diet of gelatinous zooplankton where patches of high prey availability are rare. These results indicate that in their first year after nesting, leatherback turtles do not fit the general model of migration where responses to resources are suppressed during transit. However, their behavior may be different in their sabbatical years away from nesting beaches. Our results highlight the importance of whole-ocean fishing gear regulations to minimize turtle bycatch.

Reproduction in five sympatric batoid species (family urolophidae) from south-eastern Australia

This PhD determines the reproductive biology of five stingaree species caught as bycatch from south-eastern Australian commercial fisheries for fisheries stock assessments, ecological risk assessments, and species extinction risk evaluations.

Ecosystem relevance of variable jellyfish biomass in the Irish Sea between years, regions and water types

Monitoring the abundance and distribution of taxa is essential to assess their contribution to ecosystem processes. For marine taxa that are difficult to study or have long been perceived of little ecological importance, quantitative information is often lacking. This is the case for jellyfish (medusae and other gelatinous plankton). In the present work, 4 years of scyphomedusae by-catch data from the 2007-2010 Irish Sea juvenile gadoid fish survey were analysed with three main objectives: (1) to provide quantitative and spatially-explicit species-specific biomass data, for a region known to have an increasing trend in jellyfish abundance; (2) to investigate whether year-to-year changes in catch-biomass are due to changes in the numbers or in the size of medusa (assessed as the mean mass per individual), and (3) to determine whether inter-annual variation patterns are consistent between species and water masses. Scyphomedusae were present in 97% of samples (N=306). Their overall annual median catch-biomass ranged from 0.19 to 0.92gm-3 (or 8.6 to 42.4gm-2). Aurelia aurita and Cyanea spp. (Cyanea lamarckii and Cyanea capillata) made up 77.7% and 21.5% of the total catch-biomass respectively, but species contributions varied greatly between sub-regions and years. No consistent pattern was detected between the distribution and inter-annual variations of the two genera, and contrasting inter-annual patterns emerged when considering abundance either as biomass or as density. Significantly, A.aurita medusae were heavier in stratified than in mixed waters, which we hypothesize may be linked to differences in timing and yield of primary and secondary productions between water masses. These results show the vulnerability of time-series from bycatch datasets to phenological changes and highlight the importance of taking species- and population-specific distribution patterns into account when integrating jellyfish into ecosystem models.

Pan-atlantic analysis of the overlap of a highly migratory species, the leatherback turtle, with pelagic longline fisheries

Large oceanic migrants play important roles in ecosystems, yet many species are of conservation concern as a result of anthropogenic threats, of which incidental capture by fisheries is frequently identified. The last large populations of the leatherback turtle, Dermochelys coriacea, occur in the Atlantic Ocean, but interactions with industrial fisheries could jeopardize recent positive population trends, making bycatch mitigation a priority. Here, we perform the first pan-Atlantic analysis of spatio-temporal distribution of the leatherback turtle and ascertain overlap with longline fishing effort. Data suggest that the Atlantic probably consists of two regional management units: northern and southern (the latter including turtles breeding in South Africa). Although turtles and fisheries show highly diverse distributions, we highlight nine areas of high susceptibility to potential bycatch (four in the northern Atlantic and five in the southern/equatorial Atlantic) that are worthy of further targeted investigation and mitigation. These are reinforced by reports of leatherback bycatch at eight of these sites. International collaborative efforts are needed, especially from nations hosting regions where susceptibility to bycatch is likely to be high within their exclusive economic zone (northern Atlantic: Cape Verde, Gambia, Guinea Bissau, Mauritania, Senegal, Spain, USA and Western Sahara; southern Atlantic: Angola, Brazil, Namibia and UK) and from nations fishing in these high-susceptibility areas, including those located in international waters.

Overlap between flesh-footed shearwater Puffinus carneipes foraging areas and commercial fisheries in New Zealand waters

Although the flesh-footed shearwater Puffinus carneipes is a species with large population sizes (tens of thousands of breeding pairs) and widespread sub-tropical distribution across Australasian water masses, it is among the species most threatened by longline fisheries mortality in this region. While bycatch mitigation measures have been very successful in reducing mortality in some species, bycatch of flesh-footed shearwaters is still high, with captures estimated to exceed the sustainable take of 514 birds yr-1 by nearly 200 birds for New Zealand fisheries alone. Management agencies aiming to reduce the impact of fisheries mortality on the populations need to understand which marine areas are being used by flesh-footed shearwaters to better target fishery monitoring and mitigation efforts. Foraging studies of seabirds tell us about their use of resources, i.e. the way species segregate the available habitat and help to identify threats that may affect population viability. Breeding shearwaters were tracked from 2 New Zealand colonies using GPS loggers. Individuals foraged over shelf and deep oceanic waters up to 1200 km from their nesting sites during incubation but were mainly within 370 km during early chick rearing. The intensity of potential interactions increased for trawl and surface longline fishing between the January and February study periods but remained at a similar level for bottom longline fishing. Following the field data collection, changes to fishery monitoring were implemented in the areas where shearwaters foraged.